A particle having mass $\mathrm{m}$ and change $\mathrm{q}$ is released from the origin in a region in which electric field and magnetic fields are given by $\overrightarrow{B}=-B_0\hat{\mathrm{j}}$ and $\overrightarrow{E}=E_0\hat{\mathrm{k}}$. The speed of the particle as a function of its $z$-coordinate is